Low-cost periodic permanent magnet and electrostatic focusing scheme for electron tubes

ABSTRACT

An improved traveling wave tube and method of manufacturing same is disclosed. The tube has an elongated housing with a central evacuated passageway. There are a plurality of beam focusing annular magnets supported within the housing around the passageway at predetermined spaced locations along the length of the passageway and a slow wave circuit supported within the housing in predetermined relationship with respect to the magnets. The housing is a pair of joined semi-cylindrical mating ceramic substrate halves, each half including semi-annular grooves along its part of the passageway which register with respective semi-annular grooves of the other half to define annular grooves which receive and support the magnets. The ceramic substrate halves have conductive material deposited therein that forms the slow wave circuit. The associated method comprises the steps of forming first and second semi-cylindrical substrate halves with rib-like constrictions and recesses for the slow wave circuit and grooves for the magnets, depositing the slow wave circuit in both halves providing magnets in the grooves; and joining the halves together with the grooves and slow wave portions on both halves in registration.

United States Patent (I91 Baker et al.

[ 1 Sept. 30, 1975 1 LOW-COST PERIODIC PERMANENT MAGNET AND ELECTROSTATIC FOCUSING SCHEME FOR ELECTRON TUBES [75] inventors: Halsted W. Baker, Forked River;

Arthur H. Gottfried, Rumson both of NJ [73] Assignee: The United States of America as represented by the Secretary of the Army, Washington. DC,

1221 Filed: Aug. 15, I974 [21] Appl. No: 497,787

3 7(15 3Z7 12/1972 Scott... 3.787.747 1/1974 Scottm. 315/35 33093-19 5/1974 Scott 1 1 a 1 v a v v 1, 315/35 Primary Exuminer-Suxfield Chatmon, Jr. Attorney, Agent or Firm-Nathan Edelberg; Robert P. Gibson; Arthur L. Bowers 15 7 1 ABSTRACT An improved traveling wave tube and method of manufacturing same is disclosed. The tube has an elongated housing with a central evacuated passageway, There are a plurality of beam focusing annular mag nets supported within the housing around the passageway at predetermined spaced locations along the length of the passageway and a slow wave circuit supported within the housing in predetermined relationship with respect to the magnets. The housing is a pair of joined semi-cylindrical mating ceramic substrate halves each half including semi-annular grooves along its part of the passageway which register with respective semi-annular grooves of the other half to define annular grooves which receive and support the magnets The ceramic substrate halves have conductive material deposited therein that forms the slow wave circuit. The associated method comprises the steps of forming first and second semi-cylindrical substrate halves with rib-like constrictions and recesses for the slow wave circuit and grooves for the magnets depositing the slow wave circuit in both halves providing magnets in the grooves; and joining the halves to gethcr with the grooves and slow wave portions on both halves in registration.

5 Claims, 5 Drawing Figures US. Patent Sept. 30,1975 Sheet 1 of2 3,909,651

U.S. Patent Sept. 30,1975 Sheet 2 of 2 3,909,651

LOW-COST PERIODIC PERMANENT MAGNET AND ELECTROSTATIC FOCUSING SCHEME FOR ELECTRON TUBES The invention described herein may be manufactured and used by or for the government for governmental purposes without the payment of any royalties thereon or therefor.

FIELD OF THE INVENTION This invention relates to improved construction and method of manufacture of traveling wave tubes.

BACKGROUND OF THE INVENTION Traveling-wave tubes (TWTs) conventionally include an evacuated housing in which a beam of electrons is projected axially from a cathode to a collector through a section of a waveguide. Micro-wave energy amplification results from interaction between the electron beam and the axial component of electrical field ofa microwave energy wave propagated through an internally provided slow wave circuit. TWTs are characterized by complexity and high cost.

SUMMARY OF THE INVENTION In contradistinction to the prior art, the instant invention concerns a less complex and lower cost travelingwave tube which comprises an elongated housing having a central evacuated passageway therethrough, slow wave circuit means supported within the housing and a plurality of annular magnets supported within the housing at predetermined spaced locations along the length of the passageway. In this invention and the overall supporting arrangement for the permanent magnets is materially simplified.

In accordance with a further feature of the invention, the tube housing comprises a pair of generally semicylindrical mating ceramic substrate halves, each half including semi-annular grooves along the interior thereof which register with respective semi-annular grooves on the other half to define complete annular grooves which receive and support the internally located magnets when the casing halves are joined to one another. The focusing magnets may be prefabricated ring magnets or they may be formed of appropriate magnetic material sputtered or sprayed into the annular grooves in the presence of a proper magnetizing field to magnetize same. In either embodiment, the magnets are provided with protective coatings that form a shield between the magnets and the vacuum environment. The coatings prevent contamination of the vacuum environment by outgassing from the magnets. If the protective coatings are electrically conductive, the coatings on the magnet rings can be additionally utilized for electrostatic focusing of the beam by means of applying proper D.C. voltages on the conductive coatings to complement the magnetic focusing.

As a further feature of the invention, and as will be further apparent, the aforementioned casing halves may be formed with circular constrictions and recesses extending between the constrictions conductive mate rial deposited in the form ofa ring-bar type circuit such that the internal circuitry is economically formed.

Accordingly, it is an object of the instant invention to provide a lower cost, less complex traveling-wave tube in which focusing magnets are located internally of the vacuum envelope and, therefore, closer to the beam.

Another object of the instant invention is to provide such tube in which the tube housing is formed of a pair of generally mating ceramic substrate halves, each half including semi-annular grooves which cooperate to receive and support internally located permanent magnets.

Still another object of the instant invention is to provide such a tube in which the ceramic substrate halves of the housing are configured such that slow wave circuitry may be deposited therein.

Yet another object of the instant invention is to provide a method of manufacture for such tubes.

These and other objects of the instant invention will be apparent by referring to the following specification and drawings.

BRIEF DESCRIPTION OF THE VIEWS OF THE DRAWINGS FIG. 1 is a perspective view, partially in section, of a portion of the length of one of the two mating halves of a traveling wave tube constructed in accordance with the instant invention.

FIG. 2 is a perspective view of the magnets and slow wave circuit, separate from the housing, employed within the tube of the instant invention.

FIG. 3 is a sectional view of the tube of the invention taken along the line 3-3 of FIG. 5.

FIG. 4 is a sectional view of the tube of the invention taken along the lines 4-4 of FIG. 5.

FIG. 5 is a cross section view of a portion of the length of the tube of the invention taken along the lines 5-5 of FIG. 4.

DETAILED DESCRIPTION Turning to the figures wherein like numerals are used to designate like elements, there is shown in the drawings, a length segment 10 of a traveling-wave tube constructed in accordance with the invention, it being understood that such conventional elements as the cathode and collector positioned at opposite ends of the tube, etc., have been eliminated for the sake of drawing simplicity. The tube housing consists of two generally semi-cylindrical mating ceramic substrate halves I2 and 14 which, are joined, as by brazing. and together define an axial, passageway for the electron beam.

The interior of the housing halves l2 and 14 are provided with semi-annular grooves 16 in axial 18 which support and alignment periodic permanent magnet rings 20, of suitable magnetic material such as samarium-cobalt, which focus the electron beam from the cathode at one end to the collector at the other end. Preferably, the magnets are covered with a coating to shield the vacuum environment against contamination by outgassing from the magnets. The coating may comprise a non-conductive material such as aluminum oxide sprayed thereon. Alternatively, the magnet coatings may be conductive material such as tungsten. copper or molybdenum so that the coatings can be utilized for electrostatic focusing by placing the proper D.C. voltages on the coatings with respect to the slow wave circuit yet to be described to complement the magnetic focusing.

Alternatively. rather than employing prefabricated magnets, magnets can be formed by depositing, as by sputtering or spraying, magnetizable material into the grooves I6 and 18 in the presence of a magnetizing field to magnetize the material. If a protective coating is employed, the grooves 16 and 18 may be sprayed with the protective material before the magnetic material is deposited, and then the exposed surfaces of the deposited magnetic material are sprayed once again with the protective coating, before the halves l2 and 14 are joined.

As also seen from the drawings, the mating surfaces 22 and 24 of the halves l2 anu 14 of the housing are formed with slow wave circuit in the form of generally V-configured recesses 26 and 28 and the inwardly directed surfaces of passageway constriction ribs 30 onto which surfaces the conductive material 32 is deposited to form a slow wave circuit having the configuration appropriate for the particular tube. Although the hous ing halves l2 and 14 may be cast and machined ceramic, it is preferred that they be manufactured by a casting technique.

Although the invention has been described with respect to a circular traveling wave tube, it will be appreciated that it may be practiced on traveling wave tubes of other configurations such as rectangular, oval or the like.

What is claimed is:

1. In a traveling wave tube that has an elongated housing for providing a longitudinal evacuated passageway for an electron beam, a plurality of electron-beamfocusing annular magnets supported within said housing along the length of the passageway, and slow wave circuit means supported along the length of the passageway for transfer of energy between an electron beam traversing the passageway and the slow wave circuit means, the improvement in the traveling wave tube that comprises,

the portion of said housing supporting said magnets and said slow wave circuit means being of nonconductive non-magnetic material and being formed of two longitudinal parts having planar faces sealed together to form an interface that is essentially coplanar with the axis of the passageway,

said housing being formed along the length of the passageway with axially spaced circular rib-like constrictions and the planar face of at least one of the longitudinal parts of the housing being formed with recesses between every two consecutive constrictions, said recesses being of generally U- configuration, one of the recesses extending from the inner edge of a first constriction normal to the axis for a predetermined distance, then parallel to the axis, and then normal to the axis to the inner edge of the second constriction,

the succeeding recess between the second and third constrictions being substantially the same as but in the direction opposite to the first recess relative to the axis,

successive U-configured recesses alternating on opposite sides of the axis, and

said slow wave circuit means being conductive material filling all said recesses and lining the inwardly directed faces of all said constrictions of both housing parts.

2. In a traveling wave tube as defined in claim 1 wherein said housing is formed with coaxial annular grooves on the interior thereof alternating with said constrictions, wherein said magnets are nested.

3. In a traveling wave tube as defined in claim 2 wherein said housing comprises a pair of generally semi-cylindrical mating ceramic substrate halves.

4. In a traveling wave tube as defined in claim 3 wherein each of said magnets are provided with a con ductive coating whereby electrostatic focusing voltage may be applied between said focusing magnets and said slow wave circuit means.

5. In a traveling wave tube as defined in claim 4, wherein said magnets are of magnetic material formed in place in the grooves. 

1. In a traveling wave tube that has an elongated housing for providing a longitudinal evacuated passageway for an electron beam, a plurality of electron-beam-focusing annular magnets supported within said housing along the length of the passageway, and slow wave circuit means supported along the length of the passageway for transfer of energy between an electron beam traversing the passageway and the slow wave circuit means, the improvement in the traveling wave tube that comprises, the portion of said housing supporting said magnets and said slow wave circuit means being of non-conductive non-magnetic material and being formed of two longitudinal parts having planar faces sealed together to form an interface that is essentially coplanar with the axis of the passageway, said housing being formed along the length of the passageway with axially spaced circular rib-like constrictions and the planar face of at least one of the longitudinal parts of the housing being formed with recesses between every two consecutive constrictions, said recesses being of generally Uconfiguration, one of the recesses extending from the inner edge of a first constriction normal to the axis for a predetermined distance, then parallel to the axis, and then normal to the axis to the inner edge of the second constriction, the succeeding recess between the second and third constrictions being substantially the same as but in the direction opposite to the first recess relative to the axis, successive U-configured recesses alternating on opposite sides of the axis, and said slow wave circuit means being conductive material filling all said recesses and lining the inwardly directed faces of all said constrictions of both housing parts.
 2. In a traveling wave tube as defined in claim 1 wherein said housing is formed with coaxial annular grooves on the interior thereof alternating with said constrictions, wherein said magnets are nested.
 3. In a traveling wave tube as defined in claim 2 wherein said housing comprises a pair of generally semi-cylindrical mating ceramic substrate halves.
 4. In a traveling wave tube as defined in claim 3 wherein each of said magnets are provided with a conductive coating whereby electrostatic focusing voltage may be applied between said focusing magnets and said slow wave circuit means.
 5. In a traveling wave tube as defined in claim 4, wherein said magnets are of magnetic material formed in place in the grooves. 